I want to update the FISHPUBCONTEXT element of an existing publication object.  When i pass in this to the SetMetaData method in the API

<ishfields>

<ishfield name="FISHPUBCONTEXT" level="version">

<features>
<feature name="featureA" value="aaa" />
<feature name="featureA" value="bbb" />
<feature name="featureA" value="ccc" />
<feature name="featureA" value="ddd" />
</features>

</ishfield>

</ishfields>

and then do a GetMetaData method call I get an empty value.

<ishobjects>

<ishobject ishversionref="341111" ishlogicalref="340867" ishref="GUID-79E18F3E-5299-405E-9D6D-C82E2A2D092C" ishtype="ISHPublication">

<ishfields><ishfield name="FISHPUBCONTEXT" level="version">
</ishfield></ishfields></ishobject></ishobjects>

How can I set the FISHPUBCONTEXT of a publication object through the API?